The present invention relates to machine tool cooling and to systems for supplying coolants to tools for cutting and other operations of manufacturing machines, and more particularly to systems and methods for connecting or disconnecting a supply of a cryogenic fluid to or from a cryogenic cooling means mounted on a machine component, such as a turret.
As used herein, the term “manufacturing machine” includes but is not limited to: machine tools—vertical and horizontal turret lathes with vertical and horizontal turret plates, vertical and horizontal milling machines with automatic tool change-over systems, and derivatives thereof; single or multi-wheel grinding machines, single or multi-spindle drilling machines, and similar vertical machining centers; and other machines with automatic tool changers—punching presses, thermal spray systems, welding systems, laser cutting, welding, and surfacing systems, etc.
Prompted by environmental, productivity, and cost-reduction pressures, the manufacturing industry continues to look for improved tool cooling methods and systems. Research and development work during the last decade has shown that the use of inert, compressed cryogenic fluids as coolants may result in certain benefits if a delivery system for such coolants and a fluid-flow line connection system are fully integrated with existing machine tools and the associated moving components that hold tools. Therefore, there is a need in the manufacturing industry for such a connection system.
Conventional coolant connection systems have been used for many years, and there are various types of cryogenic connectors or couplings. However, there does not exist a fully functional cryo-fluid coolant connection system for modem manufacturing machines, especially machines that are controlled by a computerized numerical controller (CNC).
Examples of coolant delivery systems for tools mounted on turret lathes are disclosed in U.S. Pat. No. 6,179,692 (Hara), U.S. Pat. No 5,265,505 (Frechette), and U.S. Pat. No 5,862,833 (Perez). However, the way that the conventional coolant passages are routed through turret plates and turret carriages in these patents, as well as the way that disconnectable passages are sealed, would be unacceptable in the case of cryogenic fluid coolants for the following reasons: (1) turret plates would thermally shrink, thereby affecting the dimensional accuracy of parts produced, (2) turrets and supporting machine components would frost during operation, leading to corrosion, (3) connections would either leak or seize, resulting in system malfunction or failure, and (4) the period of time required to cooldown the passages from ambient temperature (e.g., room temperature) to the temperature of the cryogenic fluid would be unacceptably long in view of the time allocated to particular machining operations.
Examples of different types of quick-releasing cryogenic couplings are disclosed in WO9708486 (Jepp) and U.S. Pat. No. 6,145,322 (Odashima) and U.S. Pat. No 5,762,381 (Vogel). However, as discussed below, these cryogenic couplings cannot be used in machine tool applications without having significant problems, difficulties, and disadvantages, both technical and economic.
The design of coaxial and vacuum insulated connecting pipes and the way of sealing the pipes with a screw motion, as disclosed by Jepp, excludes the use of this system for machine tools due to connection time that would be unacceptably long, space and cost limitations, as well as the complexity of an automatic actuator that would be required.
The design of Odashima provides for an automatic plugging of line exits in the disconnected condition by two self-opposing check valves and an opening of the coupling passage by squeezing these components against each other. The face seal assembly and the check valves require that certain axial forces are applied to engage the coupling. The design comprises a number of intricate and wearing (or consumable) parts wetted by cryogenic fluid, and the overall surface area and weight of these parts would result in the cooldown time from room temperature to the temperature of the cryogenic fluid being unacceptably long in view of the time allocated to particular machining operations. In effect, this type of coupling cannot be used for an actuated connection required in the case of machine tools.
The design of Vogel also cannot be used for such an automated connection since its sealing action requires (1) axial sealing of the two ends of the line, and (2) radial quick-connect clamping, necessitating an actuating device much more complex and expensive than a simple linear actuator which would be cost-justified in machine-tool retrofit systems.
It is desired to have an apparatus and a method for connecting or disconnecting a supply of a cryogenic fluid to or from a cryogenic cooling means mounted on a moveable machine component (e.g., a turret) and spaced apart from the supply of the cryogenic fluid which overcome the difficulties and disadvantages of the prior art to provide better and more advantageous results.